The committed efforts of professional and volunteer wildlife carers, volunteer citizen scientists and City of Cockburn staff saved potentially hundreds of native freshwater turtles from death during the 2021-22 nesting season.
Populations of the ‘near threatened’ semi-aquatic Southwestern snake-necked turtle (Chelodina oblonga – prev. C. colliei
) are active throughout Cockburn including Bibra Lake, Yangebup Lake, Harmony Lake and Manning Park, and many other Perth lakes and wetland areas.
City of Cockburn Environmental Education Officer Vicky Hartill said climate change, increased predation by birds, dogs, foxes and cats plus human activity was threatening their existence in areas where the turtles once flourished.
Strategic annual planning by the City’s Environmental team, including on-the-ground Turtle Tracker squads, has reduced the species’ mortality rate by protecting nesting females and their eggs from predator attack and vehicle strike.
For six weeks during peak nesting season between September and November 2021, 14 dedicated trained volunteer Turtle Trackers conducted twice daily shifts and were on call during mass movements to record turtle and nest sightings including mortality and predation and protecting females on the move by guarding their egg-filled nests with temporary mesh coverings.
Murdoch University ran a trial that safely allowed the incubation of about 80 eggs from nests, while WA Wildlife obtained eggs from deceased and injured turtles for a similar incubation trial.
At Bibra Lake alone, they saw 124 turtles on the move, found 34 nests 12 of which had been predated, covered 26 nests with protective cages and four others with temporary mesh.
Supporting data was logged on Australia’s citizen science TurtleSAT app to help build a picture of the health of Cockburn’s turtle population.
“Turtle Trackers is the brainchild of the City and Murdoch University with PhD student Anthony Santoro,” Mrs Hartill said.
“A pilot program was developed with the help of WA Wildlife and The Wetlands Centre Cockburn in 2019 and it has proven very effective so far.”
At Manning Lake, the City conducted an opportunistic nest cover trial during a mass turtle movement observed by Parks staff onsite at the time.
While Bibra Lake was the anticipated site for the trial, it was conducted at Manning Lake during a rain event which is a popular time for female turtles to leave the water in search of soft sand to lay their eggs.
Flat mesh was staked over 21 nests and monitored daily for two weeks with minor raven disturbance noted. The covers were eventually removed in readiness for hatchlings to emerge around 220-240 days later.
Hatchlings may be seen from late June onwards and people are urged to safely help them to water.
No interference or predation was observed and the method will be trialled and studied further this year.
Between July and October 2021, 56 turtles were admitted to WA Wildlife, some via TurtleTracker volunteers, with a 70 per cent survival rate.
Of these, 17 had died or needed to be euthanised including 12 due to predation and seven as a result of vehicle strike.
“While the peak of turtle nesting season has finished, nesting can continue throughout January, especially around dusk,” Mrs Hartill said.
“We ask residents continue to report observations of turtle movements and nesting using the TurtleSAT App.”
City actions to help protect nesting females during the 2021-22 nesting season:
What should you do if you see a turtle on the move:
- Feral animal control in and around turtle nesting areas in conjunction with the Department of Biodiversity, Conservation and Attractions
- Turtle information sessions attended by 90 people
- Mowing delayed during nesting season to minimise turtle deaths and provide protection from predators
- Installation of temporary educational signage – ‘turtles on the move’, ‘keep dogs on-leash’ and ‘slow down for turtles’
- Turtle Trackers program to help protect turtle nests at Bibra Lake
- Collaboration with Murdoch University to deliver turtle, egg and fauna underpass monitoring
- Feasibility studies to install a custom designed fauna underpass on Progress Drive
- Maintaining 12 lakeside nesting refuges at Bibra Lake
- Installing traffic education message boards.
- They are not lost – if they need help, assist them in the direction they were heading
- Drive slowly around wetlands
- Protect them from predators. It is best to keep your distance, but wave off ravens and other birds if they are attacking
- Take any injured or dead turtles to WA Wildlife (formerly Native ARC), 172 Hope Road, Bibra Lake. Eggs can be retrieved for incubation
- Turtle hatchlings can be taken straight to the water
- Keep a box and towel in your car for turtle season
- Log sightings on the TurtleSAT app.
Visit the City’s Turtle webpage
to find out more about the local species.